Milling apparatus



Nov. 15, 1955 D. E. MARSHALL MILLING APPARATUS Filed July so, 1953 7 Sheets-Sheet l Nov. 15, 1955 D'. E. MARSHALL 2,723,422

MILLING APPARATUS Filed July 50, 1953 7 Sheets-Sheet 2 a: I a jlili I Nov. 15, 1955 D. E. MARSHALL MILLING APPARATUS 7 Sheets-Sheet 3 Filed July 50, 1953 I 3640 Jam/JIM? a// Nov. 15, 1955 D. E. MARSHALL 2,723,422

MILLING APPARATUS Filed July so, 1955 V 7 Sheets-Sheet 4 Illl llllll 'SMW Nov. 15, 1 D. E. MARSHALL MILLING APPARATUS 7 Sheets-Sheet 5 Filed July 50, 1953 1 1955 D. E. MARSHALL 2,723,422

MILLING APPARATUS Filed July 30, 1955 7 Sheets-Sheet 6 7 igf v Nov. 15, 1955 D. E. MARSHALL MILLING APPARATUS 7 Sheets-Sheet '7 Filed July 30, 1953 Jaw/d .Z". Mars/75H MILLING APPARATUS Donald E. Marshall, Edina, Minm, assignorto Micro Processing Equipment Inc., Des Plaines, Ill., a corporation of Illinois Application July 30, 1953, Serial No. 371,313

23 Claims. (Cl. 18-2) This invention relates to milling apparatus and refers more particularly to a machine for milling in the sense this term is used in the soap making art. In this sense milling consists in mechanical refinement of the material being acted upon to bring about improved physical properties chiefly as a result of particle size reduction which in soap results in smoother texture, greater durability and better solubility and lathering.

It should be understood, however, that though the apparatus of this invention was developed for the soap industry its use is not limited thereto. Rubber, plastics, chocolate and paint pigments are some of the many products that can be milled with the machine of this invention, not only better than was heretofore possible but also at a fraction of the cost, especially in powerconsumption.

Prior to the discoveries upon which rests the technique described in Patent No. 2,619,680 issued to Donald Marshall and Patent No. 2,620,511 issued to Donald E. Marshall of al., it was thought that satisfactory milling of soap and other materials having comparable physical properties could be accomplished with conventional roller mills, so-called Banbury mixers and extrusion type mixers. It is now known, however, that machines of that nature are utterly incapable of producing the particle size reduction which the inventions of the aforesaid patents have demonstrated to be necessary for the attainment of the desired refinement. As fully explained in the said Marshall and Marshall et al. patents, it is only when the particles in mass have been reduced to a submicron state of subdivision by a rapid internal shearing action that the results sought can be accomplished.

To achieve this fine degree of subdivision the material must be subjected to an internal shearing and compacting action brought about by passage thereof under pressure through a milling zone defined by complementary relatively moving milling surfaces of substantial area spaced apart a uniform distance on the order of .002 to .030 of an inch. This imparts relative movement between. the surface layers at the opposite sides of the filmlike sheet of material in the milling zone which in turn produces the internal shearing and compacting.

While the technique taught and covered by the aforesaid patents was capable of producing the desired results, the apparatus disclosed therein was incapable of taking full advantage of this new technique. It is thus the purpose and object of this invention to provide an apparatus by which the technique taught and covered in the said Marshall and Marshall et al. patents can be more efiicaciously practiced.

Since the extent of the shearing accomplished by the technique taught in the aforesaid patents is a function of the viscosity of the material being acted upon and the rate of shear, it follows that optimum practice of this technique requires an apparatus capable of achieving not only the extremely fast shear rates needed to mill low viscosity materials and the very high feed pressures required to handle high viscosity materials, but in States Patent addition this apparatus must enable any desired correlation between these factors. Accordingly it is another object of this invention to provide a milling apparatus which embodies the principles of the aforesaid patents and in which feed pressures on the order of at least 4000 pounds per square inch and shear rates up to on the order of 3000 feet per minute are possible, and wherein these values are readily regulatable to adapt the machine for the most efiicient milling of different mate rials and the attainment of different end products.

While it may require pressures as high as 4000 pounds per square inch to feed some materials into the milling zone, it is obvious that pressures many times less than this obtaining in the milling zone would result in prohibitive braking of the moving milling element. Hence, it is another object of this invention to so feed the material into the milling zone that by the time it enters the milling zone its hydrostatic pressure has been reduced to an amount on the order of fifty to one hundred pounds per square inch.

The selection of the clearance between the complementary milling surfaces depends upon the nature of the work to be performed by the apparatus and since for many purposes this clearance may have to be as close as two thousandths of an inch, it is extremely important that the cooperating milling members be so designed and constructed that their milling surfaces will be maintained at the desired spacing without the need for complicated and heavy supports for the milling members despite the pressure exerted on the milling surfaces by the material being fed into and through the milling zone.

Accordingly it is one of the features of this invention that the complementary milling surfaces are annular and disposed one within the other, or in other words, are

on the opposing surfaces of a rotor and stator arranged one inside the other. With this arrangement the forces exerted against the milling surfaces are radial and thus contained wholly within the annuli of the rotor and stator.

In this connection it is a further object of this invention to so arrange the inlet into the milling zone that the material enters it radially and simultaneously around the entire circumference of the milling zone so that the feed pressure does not impose imbalancing forces of any kind upon the rotor.

To achieve the required high feed pressure a novel gear pump similar to that disclosed in the copendiug application of Donald B. Marshall, Serial No. 271,059 filed- February 11, 1952, is employed. The discharge of this pump feeds into a manifold chamber which leads to the inlet of the milling zone and since for some purposes the mechanical refinement which the material undergoes during the pumping thereof by the gear pump may be sufficient, it is another object of this invention to so construct the machine that the rotary mill may be easily disconnected from the gear pump and replaced by a suitable extrusion head having an orifice of the desired shape through which the pump may extrude the material at high pressure.

One of the important features of the invention, as will be hereinafter more fully described, resides in the high volumetric efliciency of the apparatus, and to attain this efficiency this invention contemplates a novel surface configuration for the rotating or movingmilling member.

It is also an object of this invention to provide a mill of the character described which is not only capable of merely by the selection of the surface configuration and design of its complementary milling surfaces.

Still another object of this invention is to provide a milling apparatus of the character described which is not only versatile in its utility and adaptation to different products, but in addition can be used to aerate or de-aerate the products milled and maintain or produce any desired temperature in the product.

A still further object of this invention resides in the provision of means for positively preventing the fouling of the inlet into the milling zone even when materials are being handled which tenaciously tend to bridge across the inlet.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a side elevational view of the milling apparatus of this invention;

Figure 2 is a plan view thereof;

Figure 3 is a longitudinal sectional view through the mill portion of the apparatus on the plane of the line 33 of Figure 2;

Figure 4 is a view in cross section through the mill portion of the apparatus and in longitudinal section through the feed pump, said view being taken on the plane of the line 4-4 in Figure 2;

Figure 5 is a view partially in horizontal section and partially in top plan taken generally on the plane of the line 5-5 in Figure 3;

Figure 6 is a fragmentary perspective view illustrating a portion of the rotatable milling element;

Figure 7 is an enlarged fragmentary longitudinal sectional view through adjacent portions of the complementary milling members;

Figure 8 is an elevational view showing a portion of the milling surface on the rotatable milling member provided with grooving different from that illustrated in Figure 6;

Figure 9 is a view similar to Figure 7 but on a reduced scale illustrating an arrangement of grooves for the milling surfaces especially adapted to such purposes as cutting material into small pieces;

Figure 10 is a detail sectional view similar to Figure 9 illustrating still another modification of the milling members;

Figure 11 is an enlarged longitudinal sectional view through the gear pump by which the material is fed into the mill, said view being taken on the plane of the line 1111 in Figure 4;

Figure 12 is a perspective view of a clean-out plug used in cleaning the mill of material which may have been left therein;

Figure 13 is a fragmentary sectional view through the mill illustrating the manner of using the clean-out plug illustrated in Figure 12;

Figure 14 is a perspective view of an extrusion plate adapted to be used in conjunction with the rotary mill to adapt the same for the extrusion of material therefrom without passage through the milling zone;

Figure 15 is a detail view illustrating how the apparatus can be transformed to straight extrusion directly from the high pressure feed pump;

Figure 16 is a longitudinal sectional view illustrating a rotary mill of modified construction; 7

Figures 17, 18 and 19 are longitudinal sectional views through a sufficient portion of the rotary mill to illustrate 4 the use of milling members having different shaped milling surfaces;

Figure 20 is a detail sectional view through Figure 19 on the plane of the line 2020; and

Figure 21 is a cross sectional view through a portion of the rotatable milling member illustrating how additional extended surface may be provided if desired.

Referring now particularly to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numerals 5 and 6, respectively, designate the mill and the feed pump of the machine of this invention. Both units are mounted upon a common base 7 and each has its own drive. The mill 5 is driven by an electric motor 8 connected to the mill through a variable speed power transmission 9 and the pump is driven by an electric motor 10 mounted below the top of the base and drivingly connected to the pump through a suitable transmission including a gear reduction unit 11.

The material to be milled is deposited in a hopper 12 provided with a removable cover 13 and fed into the pump 6 by a screw type feeder 14. The screw of the feeder 14 is driven by a motor 15 drivingly connected to the screw through a variable speed drive transmission 16. The feeder 14 is of conventional construction and its screw operates in a tapered barrel 17, the discharge end of which is connected to the pump as best shown in Figure 4.

To regulate the temperature of the material being fed to the pump by the feeder, its barrel 17 is equipped with coils 19 through which a fluid temperature modifying medium may be circulated. Ordinarily the fluid circulated through these coils is a coolant fed thereto from any suitable source as for instance a pump, not shown, mounted in the base 7.

The pump 6 must be capable of pumping very high viscosity materials such as soap in the solidified state, and to deliver such material at a satisfactory rate, as for instance 2000 pounds per hour, requires a pressure on the order of 4000 pounds per square inch. Pumps heretofore available were incapable of such performance, and accordingly the very special gear pump 6 was developed. As shown, the body of the pump has a central substantially oval shaped cavity 20 in which meshing gears 21 and 22 operate with close clearance. These gears are of the herringbone type and are carried by heavy shafts 23 and 24, respectively, the diameter of the shafts being but slightly less than the root diameter of the gears. The shafts are journaled in bearing bushings 25 seated in inserts 26 which fill the opposite end portions of the oval shaped cavity 20 and are held in position against the opposite faces of the meshing gears by cover plates 27. One of the cover plates has the shaft 23 protruding therethrough to be drivingly connected to the output shaft of the transmission 11.

An inlet 28 leads to one side of the cavity 20 and an outlet 29 leads from the other side thereof so that the gears, in revolving in the directions shown by the arrows in Figure 4, continually transport or convey the material fed into the inlet 28 by the feeder 14 in small increments to the discharge or outlet port 29.

Since the gears are of the herringbone type it is evident that as they move into mesh the material which has been transported in the spaces between the teeth is forced therefrom and discharged into the outlet 29 which, of course, is solidly filled at all times since it discharges against substantial back pressure.

By virtue of the fact that the gear teeth, or more specifically the spaces therebetween, convey the material in small increments with a positive pumping action the temperature rise which the material undergoes in being forced through and from the pump is not serious and can be readily held to an inconsequential minimum by circulating a coolant through passages 30 formed in the body of the pump, and which may be connected in circuit with the coolant source mentioned before.

A duct 31 connects the outlet of the pump with the inlet 32 of the mill '5. This duct is preferably provided with a thermometer 33 and a pressure gage 33" to indicate the temperature and pressure of the material moving into, the mill. The gage shown is of the type wherein a piston operating in a cylinder connected with the pressure source is yieldingly held down by a weight on a pivoted lever connected with the piston.

The mill 5 consists essentially of a rotor 34 revolving within E1v stator 35', mounted on one end of a bearing housing 36 which in turn is bolted or otherwise secured to the base 7'. The stator comprises an annulus 37 having an annular manifold chamber 38 formed therein and communicated at diametrically opposite sides with the material inlet 32 and'an outlet port 39 which is normally closed by a removable cover plate 40. Adjacent to the inlet and outlet ports 32 and 39 the annulus'has diametrically opposite mounting legs 4 1 formed thereon and extended axially therefrom to be bolted as at 42 to an'endyplate 4-3 secured to the bearing housing 36.

In cross section the annulus 37 is so shaped that its manifold passage 38 has converging inwardly directed side walls 44 the inner edges of which are spaced apart to define an annular slit-like discharge orifice 45 which leads from the manifold chamber about the entire inner circumference thereof except where a few circumferentially short cross ribs 44 tie the walls 44 together and hold them from being spread apart.

The annulus 37 is hollow around its manifold chamber to provide for the circulation of a suitable fluid temperature modifying medium, ordinarily a'liquid coolant, which enters through a port 47 and leaves through a port 47", these ports being suitably connected with the heretofore mentioned coolant source (not shown). Cooling fins 46 are preferably formed integrally with the walls of the manifold chamber to extend into the hollow interior of the annulus and improve the heat transfer.

The inner surface of the annulus 37 to which the slitlike orifice 45 opens is cylindrical and seated on this cylindrical surface are two endwise spaced milling membars or rings 48, the bores of which are cylindrical and smooth surfaced.- These milling members are identical and have an outer diameter to snugly fit the inner cylindrical surface of the annulus and have annular attaching flanges 49 which are received in complementary shaped grooves in the opposite sides of the annulus. Screws 50 pass through these flanges-andare threaded into the body of the annulus to secure themilling members or rings 48 in position.

The space between the adjacent edges of the milling members or rings 43 aligns with the slit-like orifice 45 and forms the actual mouth of the orifice; and attention is especially directed tothe fact that thisannular space, or mouth of the discharge orifice, is equispaced from the opposite edges of the milling members 48 which are beveled as at 51 to conically enlarge their bores.

The rotor 34 comprises a hollow annulus 52 having a hub 53' which is mounted on and keyed to a heavy drive shaft 54. A nut 55 threaded on the outer end of the drive shaft 54 clamps the rotor against a spacer 56 interposed between the rotor and a shoulder formed by an enlargements? on the shaft. In this manner the thickness of the spacer determines the axial position of the rotor with respect to the stator so that different width rotors can be accommodated and properly aligned with thestator by merely selecting a spacer of the correct thickness. For a purpose to be later described the spacer as well as the rotor is keyed to the shaft.

Beyond, its enlargement 547 the shaft is mounted in and supported by two roller bearings 57the outerfrings of which are seated in the bearing housing 36; and a. flexible coupling 58 connects the extreme inner end of the shaft with the output shaft of the variable speed drive transmission 9.

The hollow annulus 52 has a cylindrical, peripheral surface and a pair of removable milling members 59 are mounted thereon in substantially the same way as the milling members 48 are mounted on the stator. The milling members 59 are identical and each has a grooved cylindrical peripheral surface which provides the milling face thereof and a beveled edge 60. These milling memhere are secured to the annulus 52 from opposite sides thereof by fastening screws 61, and clamped between their adjacent inner edges is a flat ring 62. Dowels 63 passing through the ring 62 and seated in aligned holes in the milling members not only secure the ring against turning relative to the milling members and the annulus 52 but also serve to properly locate the milling members with respect to one another, such proper location being necessitated by the fact that the grooves 64 in the surfaces of the milling members should have their adjacent ends in alignment.

The ring 61 has a pair of diametrically opposite rake teeth 61' projecting therefrom and into the mouth of the slit-like discharge orifice but not far enough to collide with the ribs 44, to recurrently travel along the circumferential length of this orifice as the rotor turns and thereby continuously break up any material tending to clog the orifice. This assures a non-fouling entrance into the milling zone which, of course, consists of the clearance between the cylindrical surfaces of the stationary and rotatable milling members.

Since the milling zone is defined by cylindrical surfaces the forces exerted thereon by the pressure of the material therein are essentially radial and thus easily contained within the rotor and stator annuli. Also, since the material enters the milling zone simultaneously about the entire circumference thereof the pressure of the incoming material is balanced around the entire rotor and no tendency to bend the rotor axis exists; and inasmuch as the entrance of the material into the milling zone is equidistant from the two outlets of the zone defined by the beveled outer edges 51 and 60 of the stator and rotor milling members any end thrust imposed upon the milling surfaces by the frictional drag of the material moving through the milling zone is nullified since the forces thus engendered are opposite and equal.

The extent of the clearance between the complementary milling surfaces is determined by'their relative diameters and depending upon the nature of the Work to be performed may be as little as .002 of an inch or as much as .030 of an inch, the selection being made by substituting one set of milling members with another. These milling members, therefore, may be considered expendable and replaceable insert rings.

The grooves 64, as best shown in Figure 7, extend outwardly in opposite directions from the inlet of the milling zone at the center thereof and for the milling of such material as soap diminish in depth and terminate short of the beveled outer edges 60. Beyond this point the cylindrical surface of the milling members is smooth and unbroken either for the remainder of the distance to the beveled edge 69, or, as in that embodiment of the invention shown particularly in Figures 6 and 7, additional short grooves 66 may extend across the junction of the cylindrical and beveled surfaces of the milling members.

All of the grooves, and especially the grooves 64, are disposed at an. oblique angle, approximately thirty degrees, to the rotor axis and lagging or impositive with respect to the direction of rotation so that the flights definedby the lands between the grooves plow the materialin the milling zone axially outwardly in opposite directions from-the center. of the zone toward both outlets thereof. This more or less positive transfer action or propulsion of the material from the inlet of the milling Zone to the outlets thereof while the material is undergoing the internal shearing and compacting manipulation described at length in the aforesaid Marshall and Marshall et al. patents, gives the mill of this invention an unprecedented volumetric efliciency.

The small grooves 66 act on the material as it discharges from the milling zone and break it up into small pieces to produce a particulated or granulated product. Where such particulating effect is not desired, the grooves 66 may be omitted as illustrated for instance in Figure 8 and in this case the material discharges from the milling zone in more or less sheet or flake-like form.

As the material discharges from the outlets of the milling zone it is swept away by triangular scrapers 67 on paddles 68 fixed to the rotor shaft, one at each side of the mill. The inner edges of these paddles also sweep closely across the surfaces of the stator annulus to continually clear the discharging material therefrom.

A collecting hood 69 enshrouds the entire mill unit and receives the material discharged from the milling zone to conduct the same into a bin 70 placed beneath the open bottom of the collecting hood. If desired a slide door or gate 71 may be provided for the outlet of the hood.

The rotor, like the stator, is preferably water jacketed and provided with extended surface fins 72 and a medial partition wall 73 which divides the hollow interior of the annulus 52 into axially spaced chambers communicated through a port 74. Fluid temperature modifying medium is conducted into one of these chambers through a duct 75 which communicates with a tube 76 disposed axially within the shaft 54 and connected with an inlet duct 77. An outlet duct 78 connects with an annular passage 79 defined by the tube 76 and the wall of the bore in which it is located, and this annular passage is in turn connected with a discharge duct 80 leading from the other chamber of the hollow annulus 52. Since part of the indicated fluid passages is in the spacer ring it is important that this ring be properly positioned on the shaft and for this reason it is keyed thereto.

It is thus possible to circulate any desired liquid temperature modifying medium through the rotor as well as the stator of the mill and thereby enable the maintenance of any desired temperature in the material undergoing treatment or, if desired, to impart any desired temperature thereto. This applies to heating as well as cooling; and

for purposes of illustration but not restriction, by using a liquid coolant of sixty degrees entering temperature it is possible with the apparatus of this invention to mill soap of very low moisture content (under eight percent) in the solidfied state and in a milling clearance of only .006 inch without having the temperature of the product rise beyond 120 F. despite the fact that a production of over 2000 pounds per hour is maintained.

If desired, additional extended surface may be pro vided for the rotor by the simple expedient of inserting rods 72' into the rotor and through its fins 72 as shown, for instance, in Figure 21.

It is, of course, obvious that since the milling members of the stator and rotor are both removable they may be readily replaced to provide any desired milling clearance and also to adapt the mill to the production of any desired end product, it being appreciated that different grooving will produce different results. Thus, for instance, an arrangement of stationary and rotatable milling elements such as shown in Figures 9 and 10 will adapt the mill to such service as cutting meat into small pieces or forming it into shreds as in conventional meat grinding. In the construction shown in Figure 9 the rotor grooves 81 are of uniform depth but are closed at their outer ends as at 82 but the stator has short grooves 83 which overlap the outer discharge ends of the grooves 81. All of the grooves are disposed at an oblique angle of approximately thirty degrees to the rotor axis and ashas been described, the angle of the grooves is such with respect to the direction of rotation that the material is propelled outwardly toward the opposite faces of the rotor and stator.

In the arrangement shown in Figure 10 the rotor grooves are again of uniform depth but extend fully across the face of the rotor while the stator has an inwardly di rected flange 84 overhanging the adjacent edge of the rotor and provided with a single row of holes 85 with which the rotor grooves successively align. The apertured flange 84 is thus quite similar to the orifice plate of an ordinary meat grinder.

Other specific shapes and arrangements of milling zones and milling surfaces are illustrated in Figures 17 to 20, inclusive, but in all of these various constructions the material to be milled is fed to the milling zone from a manifold passage in the stator through a radially inwardly opening annular slit-like orifice along which the clean-out teeth or rakes 61 travel.

In the construction shown in Figure 17 the milling zone is V-shaped in cross section defined by a rotor rim 86 running in a V-shaped groove 87 in the stator. Figure 18 illustrates a construction which combines a cylindrical milling zone designated generally by the numeral 88 with a conical milling zone 89; while in Figures 19 and 20 the milling zone is substantially the same as that of Figure 17 but in addition to the slit-like discharge orifice leading from the manifold chamber of the stator there are circumferentially spaced narrow radial discharge slits 90.

In the event the mill is left idle for any length of time with its manifold chamber 38 filled with material, it may be difficult to clean out the chamber by running the mill in the ordinary manner even though the cover plate 40 is removed to open the discharge port 39. In this case a clean-out plug 91 (see Figure 12) may be used. The plug 91 has a mounting flange 92 with a discharge port 93 therethrough at one side of the plug. When the plug is secured in place as shown in Figure 13, its inner end is contiguous to the adjacent cross rib 44 and thus blocks otf communication between one-half of the manifold chamber and the discharge port 93. The full pressure of the pump thus can be exerted upon the material in the other half of the manifold chamber, and after that half of the chamber is cleared the plug 91 may be removed, turned 180 degrees and replaced whereupon the rest of the manifold chamber may be cleared.

For some purposes, as for instance blending as distinguished from milling, it is unnecessary to have the material pass through thhe milling zone, it being sufficient to merely feed the same by means of the high pressure gear pump into the manifold chamber of the mill and from this chamber through the ports in an orifice plate 95 secured across the outlet 39 in lieu of the cover plate 40. For such purposes it may also be sutficient to entirely eliminate the mill portion of the apparatus and to sub stitute an extrusion head or nozzle 96 as shown in Figure 15. Upon removal of the mill, the extrusion nozzle may be mounted upon the discharge end of the gear pump in place of the duct 31, and while the nozzle may take various forms it preferably comprises complementary cup-shaped sections bolted together with a bafile plate 97 therebetween. The baffle plate blocks direct flow through the unit by requiring the material to flow through a series of small ports 98 located in the plate radially outwardly beyond the direct path of the material entering the nozzle.

. The discharge end of the nozzle may be shaped to extrude 7 102 defined by two conical surfaces 103 and 104, the

former having a steeper angle than the latter so that the manifold passage 102 decreases in width toward its outer periphery.

The conical surfaces 103 and 104 are on two separate members 105 and 106, respectively, which are held together by tie bolts 107 in such spaced relation as to provide an annular slit-like discharge orifice 108 at the outer periphery of the manifold passage. The width of this slit-like passage is determined by spacers 109 interposed at intervals between the members 105 and 106. Beyond the annular slit-like orifice or throat 108 the members 105 and 106 have diverging conical surfaces 110 and 111, respectively, which together define an angle bisected by a plane which is normal to the axis of the unit and bisects the slit-like orifice or throat 108.

The diverging conical surfaces 110 and 111 are the stationary milling surfaces which coact with complementary conical surfaces 112 and 113, respectively, on an annulus 114 which constitutes the essential element of the rotor. This annulus is mounted upon a rotor plate 115 by means of circumferentially spaced posts 116 and the plate 115 is in turn carried by a drive shaft 117 journaled in bearings 118, only one of which is shown. Any suitable means may be employed to drive the rotor.

Both members 105 and 106 which together comprise the stator and also the rotor annulus 114 are provided with coolant passages to permit the circulation of a liquid coolant or other temperature modifying medium, Whereby the temperature of the product being acted upon may be maintained or influenced in any desired manner.

As in the previously described embodiments of the invention the material to be milled enters the manifold chamber as a solid stream of small perimeter and under the full pressure developed by the pump. As it travels radially outwardly through the manifold chamber 102, it is preshaped into an annular or circular sheet in which shape. it enters the milling. zone defined by the clearance between the adjacent conical milling surfaces. The perimeter of this circular sheet is considerably greater than the perimeter of the stream entering the manifold chamber so that high through-put rates can be maintained and at the same time the hydrostatic pressure of the material inv the milling zone is but a small fraction of what it is upon leaving the pump.

It will also be appreciated that since the inner edge ofthe rotor annulus 114 lies on a plane normal to the rotor axis and bisecting the slit or throat 108 the preformed circular sheet of material entering the miling zone is split in two with one half moving in one axial direction and the other moving in the other axial direction. As a result the hydrostatic pressure at opposite sides of the rotor annulus is balanced and this, of course, enables the maintenance of a very close clearance between the complementary milling surfaces of the stator and rotor. The extent of this clearance depends upon the relative positions of the members 105 and 106 and this in turn is determined by the thickness of the spacers 109.

As in the previous embodiments of the invention, the milling surfaces 112 and 113 of the rotor are, grooved to effect more rapid movement of the material through the milling zone and to impart the desired shearing and compacting action upon the material as it travels through the milling zone.

In this embodiment of the invention as distinguished from those previously described the pressure upon the milling surfaces of the rotor has an axial component which is not present where the milling surfaces are only cylindrical. However, there are two such axial components, one opposing and balanced, against the other. The net result, therefore, is no different than thatv which obtains where the forces exerted against the complementary milling surfaces by the pressure of the material in the milling zone are essentially radial. The important thingis that there is no unidirectional end thrust upon the rotor, and this constitutes one of the chief distinctions between the present invention and the structure illustrated in Fig.

10 ure 19 of the aforesaid "Marshall et al. Patent No. 2,620,511 which construction may be considered the forerunner of the instant apparatus.

A very important advantage of the apparatus of this,

invention is that if desired the product obtained therewith is .easily aerated. This follows from the fact that the gear pump which feeds thematerial into the mill is gas or air tight so that gas or air may be occluded in the mass being fed to the mill simply by running the feeder 14 slower than needed to fill the pockets formed by the spaces between the gear teeth, in other words, slightly -starving the pump.

Another important feature of the invention resides in the flexibility of the apparatus in the sense of its ability to mill at wide variety of materials. Thus for instance, where extremely stiff high viscosity material such as low moisture soap in the solidified state is to be milled the full power of the pump may be used to provide the required high feed pressureperhaps 4000 pounds per square inch-and since such material does not require a fast shear rate and in fact is milled better at a relatively low shear rate, the speed of the mill rotor is reduced to perhaps 200 feet per minute.

Conversely, Where a more fluid material is to be milled, the full power'of the pump may not be needed and to achieve the desired shearing the speed of the mill rotor may be appropriately increased to run for instance at more than 2000 feet per minute.

In other words, as will be readily apparent to those skilled in the art, the apparatus. is extremely flexible and well adapted to handle a wide variety of materials and to produce a Wide variety of products. It will also be seen that the apparatus of this invention not only fulfills its main objective, namely, to provide a machine with which the technique taught in the aforesaid Marshall and Marshall et a1. patents may be more efficaciously practiced, but that it also provides a machine which is highly satisfactory by any test-safety, simplicity, ruggedness, ease of operation, relatively low manufacturing cost and above all high production or through-put coupled with very low power consumption.

What I claim as my invention is: I

1. The milling apparatus of claim 10 further characterized by the fact that the complementary milling surfaces are cylindrical.

2. The milling apparatus of claim 9 further charac terized by the fact that the stationary milling member encircles the rotatable milling member and has the feed passage in it so that the material flows radially inwardly as it enters the milling zone.

3. The milling apparatus of claim 10 further characterized by the provision of a clean-out member projecting from the rotatable milling member into said narrow annular slit to move along said slit and continuously break up material tending to bridge across the slit.

4. The milling apparatus of claim 10 further characterized by the fact that the rotatable milling member surrounds the stationary milling member and comprises an unbroken annulus having a substantially *V-shaped cross section with the apex of the V forming the inner periphery of the annulus, the angularly disposed surfaces of said rotatable milling member being symmetrical with respect to a median plane normal to the axis of rotation of the rotatable member and passing through the apex of the V and constituting the milling surfaces of the rotatable, milling member, and the milling surfaces of the stationary milling member being concentric to the angularly disposed milling surfaces of the rotatable milling member, and the communication between the feed pas sage and the milling zone being in line with the apex of the. V-shaped cross section of the rotatable milling member.

5. The milling apparatus set forth in claim 4 further characterized by the fact that one of the milling surfaces 11 of the stationary milling member is axially movable toward and from the other milling surface of the stationary milling member so that by adjustment of said milling surfaces toward and from one another the clearance between the rotatable and stationary milling surfaces is set; and means for adjusting the axial relationship between the stationary milling surfaces.

6. In milling apparatus, the structure set forth in claim 16 further characterized by the fact that the rotor rings have grooves in in their outer faces for conducting material from the outlet means of the feed passage through the milling zone in opposite axial directions, the adjacent ends of the grooves in the two rotor rings opening to the outlet means of the feed passage and the grooves being disposed obliquely across the annular faces in which they are formed with the grooves in one ring at an angle opposite that of the other ring; and means for rotating the rotatable milling member in the direction such that the adjacent ends of the grooves in the two rings lead and their remote ends trail so that the advancing faces of the grooves plow the material fed into the milling zone outwardly in opposite axial directions.

7. The article of manufacture set forth in claim 18 further characterized by the fact that said endwise adjacent milling surfaces are on separate milling rings; and the rake tooth is carried by a third relatively thin ring; and means securing said milling rings in coaxial end-toend relationship with the rake tooth ring clamped therebetween.

8. The article of manufacture set forth in claim 19 further characterized by the fact that the grooved annulus comprises a pair of endwise adjacent rings secured together with the rake tooth clamped between their adjacent ends.

9. Milling apparatus comprising: cooperating stationary and rotatable milling members, one within the other; cooperating closely spaced complementary milling surfaces on said members defining an annular milling zone between them, said surfaces being symmetrical about a median plane normal to the axis of rotation of the rotatable member, and said milling zone being open adjacent to both axial ends thereof; means fixed on the stationary milling member defining a material feed passage therein having an inlet which opens to the exterior of said member and having annular slit-like outlet means which opens radially toward the rotatable milling member and communicates with the milling zone equal distances from its axial ends so that material entering the milling zone flows therethrough in divergent directions toward the axial ends of the milling zone so as to impose substantially balanced axial forces upon the rotatable member; and the stationary walls of said feed passage converging toward said annular slit-like outlet means and cooperating therewith to preshape viscous material flowing toward the milling zone into thin annular sheet form so as to minimize the braking effect resulting from impingement of the material against the milling surfaces of the rotatable member.

10. Milling apparatus comprising: cooperating stationary and rotatable annular milling members, one within the other, means on said members providing opposed complementary annular milling surfaces coaxial with one another and defining an annular milling zone therebetween open at its axially opposite ends; means fixed with respect to the stationary milling member providing a material feed passage therein having an inlet which opens to the exterior of said stationary member, said feed passage terminating in an annular slit providing an outlet which opens radially to the milling zone at a location medially of the ends thereof so that the material entering the milling zone fiows in divergent directions therethrough toward both ends of the milling zone and thereby imposes substantially balanced axial forces upon the rotatable member; the walls of said feed passage converging radially toward said annular slit so that viscous material flowing through the feed passage under high pressure to its outlet is preshaped into a thin annular radially moving sheet as it enters the milling zone to minimize the braking effect resulting from impingement of the material against the milling surfaces of the rotatable member; means for force feeding viscous material to be milled into the inlet of said feed passage under high pressure; and means for rotating the rotatable milling member.

11. A milling apparatus of the character described, comprising: a rotor; a stator encircling the rotor; means for rotating the rotor; complementary closely adjacent annular milling surfaces on the rotor and stator, the stator having an annular manifold chamber encircling its milling surface and opening radially to its milling surface through an annular slit-like orifice, the walls of said annular manifold chamber being shaped to converge toward said annular slit-like orifice so that material being forced from the chamber through said slit-like orifice and into the milling zone is preshaped into a thin annular radially inwardly moving sheet; means defining an inlet leading into said annular manifold chamber; means for force feeding material to be milled through said inlet and into the annular manifold chamber to flow therefrom under pressure into the milling zone between said complementary milling surfaces; and a clean out tooth carried by the rotor and traveling in the inlet of the milling zone to continuously break up material tending to clog said inlet.

12. Milling apparatus of the character described, comprising: a rotor and a stator, the latter encircling the former; an inwardly facing substantially cylindrical milling surface on the stator, the stator having an annular manifold chamber therein opening to its milling surface medially of the axial ends thereof through a narrow slitlike orifice; the stator also having an inlet leading to said manifold chamber; a pair of annuli on the rotor disposed in axial side-by-side relation and each having a substantially cylindrical milling surface on its periphery positioned to sweep with close clearance across the inwardly facing substantially cylindrical milling surface of the stationary member at one side of its slit-like orifice; means for holding said annuli together; a ring encircling the rotor and clamped between its two annuli; and a tooth on said ring projecting into and traveling in said slitlike orifice.

13. The milling apparatus of claim 12 further characterized by the fact that the milling surfaces of said annuli have circumferentially spaced grooves therein, the adjacent ends of the grooves of the two annuli communicating with said narrow slit-like orifice and said grooves extending obliquely in opposite directions across the milling surfaces of the annuli toward the remote ends thereof and terminating short of said remote ends of the annuli.

14. The milling apparatus of claim 10 wherein said means for force feeding viscous material into the inlet of the feed passage comprises a gear pump having a body provided with a gear cavity and an inlet and an outlet leading to and from said cavity, and having a pair of meshing gears operating with close clearance in said cavity; means connecting the outlet of the pump with the inlet of the material feed passage; means for driving the gears of the pump; and wherein the means for rotating the rotatable milling member comprises an adjustable speed driving means, the adjustability of said driving means enabling the speed of the rotatable milling member to be correlated with the pressure at which the material is fed to the milling zone in accordance with the viscosity of the material.

15. The milling apparatus set forth in claim 9 wherein the milling surface on the stationary milling member comprises a pair of endwise adjacent rings mounted on the stationary milling member; and means removably securing said rings in place in exact coaxial alignment 13 with one another and with their adjacent ends spaced apart and the space thus provided in line with said feed passage and providing the annular slit-like outlet means of the feed passage.

16. The milling apparatus of claim 15 further characterized by the provision of a pair of endwise adjacent rotor rings encircling the rotatable milling member, the outer faces of which rotor rings provide the milling surface of the rotatable milling member; and means removably securing said rotor rings to the rotatable milling member.

17. The milling apparatus of claim 9 wherein the rotatable milling member comprises a rotor having an unbroken periphery; and further characterized by the provision of a pair of endwise adjacent rings removably mounted on said rotor and encircling its unbroken periphery, the outer annular faces of said rings providing the milling surface of the rotor, and the adjacent inner ends of said outer annular faces having the same diameter, said rings having circumferentially spaced grooves in their outer annular faces extending from the inner ends of the rings obliquely across their outer faces toward the outer ends of the rings with the angle of the grooves in one ring opposite that in the other ring.

18. As an article of manufacture, a milling element comprising: an annulus having annular endwise adjacent milling surfaces symmetrical to a median plane normal to the axis of the annulus; flights defined by circumferentially equispaced grooves in each of said milling surfaces, said grooves extending obliquely across the milling surfaces in which they are formed and converging toward said median plane at the same angle thereto, and the face of each flight which forms an obtuse angle to said median plane as measured across the width of the groove defining said flight face being substantially perpendicular to the milling surface; and a rake tooth projecting from the milling surfaces on said median plane.

19. As an article of manufacture, a set of milling elements, comprising: complementary annuli, one within the other; each of said annuli having endwise adjacent annular milling surfaces symmetrical'to a median plane normal to the common axis of the annuli with the milling surfaces of one annulus opposing and uniformly spaced from the milling surfaces of the other to define an annular milling zone, the radial dimension of which is determined by the relative diameters of said opposing surfaces; one of said annuli comprising a pair of endwise adjacent rings having their adjacent ends spaced apart to provide an annular inlet orifice opening radially into the annular milling zone medially of the axial ends thereof; and the other annulus having circumferentially equispaced grooves in its endwise adjacent milling surfaces extending obliquely thereacross and converging towards said median plane at the same angle thereto and with the converging ends of said grooves extending past the adjacent ends of said rings to communicate with the annular space therebetween; a rake tooth on the grooved annulus projecting radially beyond its milling surfaces and into the annular space between the rings of the other annulus.

20. In a milling apparatus of the character described, the combination of: cooperating rotatable and stationary milling members having closely spaced complementary annular milling surfaces of substantial area defining an annular milling zone; stationary walls defining an annular slit-like orifice leading to said milling zone; means for .pumping high viscosity material through said inlet and into the milling zone; closely circumferentially spaced grooves in the annular milling surface of the rotatable milling member, said grooves leading from the annular slit-like orifice towards an axial end of the rotatable milling surface; means at said axial end of the rotatable milling member blocking direct flow of material from the milling zone through said grooves, and small circumferentially spaced discharge passages in the stationary milling member adjacent to said axial end of the rotatable milling member positioned to communicate with said groovesas they pass to thereby receive material from the grooves and discharge the same as non-rotating axially moving shreds.

21. The combination set forth in claim 20, but wherein the means for blocking direct flow out of the grooves is provided by terminating the grooves short of said axial end of the rotatable milling member; and wherein the discharge passages comprise short grooves in the sta tionary milling member so disposed with respect to the grooves in the rotatable milling member as to have their inner ends overlap and communicate with the closed ends of the grooves in the rotatable milling member as they pass, the outer ends of said grooves in the stationary milling member being open.

22. The combination set forth in claim 20, but wherein the means for blocking direct flow out of the grooves comprises a wall on the stationary milling member overlying said axial end of the rotatable milling member; and wherein the discharge passages comprise circumferentially spaced ports in said overlying wall on the stationary milling member located to align with the adjacent ends of the grooves as they pass.

23. The milling apparatus of claim 10 further characterized by the provision of closely circumferentially spaced grooves in the annular milling surface of the rotatable milling member, said grooves terminating short of the axial ends of the milling surface of the rotatable milling member and defining flights which extend obliquely to the direction of movement of said milling surface with the angle thereof such that the flights convey material in the milling zone toward the open ends thereof, so that the flights coact with the means for force feeding the material through the feed passage and into the milling zone in moving material through the milling zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,496,641 Hurrell June 3, 1924 1,650,088 Molin Nov. 22, 1927 1,832,827 Youngblood Nov. 17, 1931 2,087,561 Tolman July 20, 1937 2,519,834 Hanson et a1. Aug. 22, 1950 FOREIGN PATENTS 605,119 Great Britain July 16, 1948 

